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Solved: IPMI interface unsuable due to vanished gateway MAC

A newer Supermicro IPMI BMCs that is temporarily without a network connection to the gateway, e.g. due to a shut/noshut of a CISCO interface port on the network path, looses its ARP information (namely the MAC of the gateway) and does not even try to recover from this state. This is due to the default "LAN interface" setting of "failover" and is cured by setting to "dedicate". This finding holds only for dedicated IPMI-Cards. Cards that share with the OS Interfaces have similiar problems that are discussed elsewhere [1].

a) How to reproduce the problem

1) Configure the IPMI Interface

The correct configuration for an IPMI interface is to give the IMPI interface :

  • an IP e.g. 10.10.10.108
  • a netmask e.g. 255.255.255.0
  • probably a MAC that is disjunct with that of the other OS interfaces e.g. 00:1b:fc:db:d2:a0
  • a default gateway IP e.g. 10.10.10.1
  • some sources [2][3] claim that the MAC of the default gateway is also needed but our findings do not support this for normal network operation. A fixed gateway MAC would be useless in the usual scenario where two gateways build a IP-Failover-System.

 

2) Ping the IPMI Interface

Go to the gateway:

$ping 10.10.10.108

PING 10.10.10.108 (10.10.10.108) 56(84) bytes of data.                                                                                                           
64 bytes from 10.10.10.108: icmp_req=1 ttl=64 time=2002 ms                                                                                                       
64 bytes from 10.10.10.108: icmp_req=2 ttl=64 time=993 ms                                                                                                        
64 bytes from 10.10.10.108: icmp_req=3 ttl=64 time=0.265 ms                                                                                                      
64 bytes from 10.10.10.108: icmp_req=4 ttl=64 time=0.355 ms

3) Disrupt the layer 2 network connection between IPMI interface an Gateway

Inqbus_S3#conf t

Enter configuration commands, one per line.  End with CNTL/Z.
Inqbus_S3(config)#int Gi0/21
Inqbus_S3(config-if)#shut
Inqbus_S3(config-if)#end
Inqbus_S3#

4) Ping the IPMI Interface

$ping 10.10.10.108

PING 10.10.10.108 (10.10.10.108) 56(84) bytes of data.                                                                                                          
From 10.10.10.1 icmp_seq=1 Destination Host Unreachable
From 10.10.10.1 icmp_seq=2 Destination Host Unreachable
From 10.10.10.1 icmp_seq=3 Destination Host Unreachable
From 10.10.10.1 icmp_seq=4 Destination Host Unreachable

5) Restore the layer 2 network connection between IPMI interface an Gateway

Inqbus_S3#conf t      
Enter configuration commands, one per line.  End with CNTL/Z.
Inqbus_S3(config)#int Gi0/21
Inqbus_S3(config-if)#no shut
Inqbus_S3(config-if)#end

6) Ping the IPMI Interface

$ping 10.10.10.108

PING 10.10.10.108 (10.10.10.108) 56(84) bytes of data.                                                                                                          
From 10.10.10.1 icmp_seq=1 Destination Host Unreachable
From 10.10.10.1 icmp_seq=2 Destination Host Unreachable
From 10.10.10.1 icmp_seq=3 Destination Host Unreachable
From 10.10.10.1 icmp_seq=4 Destination Host Unreachable

 

b) How to solve the problem

 

1) Reboot the IPMI Server

2) Use the Webinterface of the IPMI-Port

Goto -> Configuration -> Network

Select from Listbox "Lan interface" the option "dedicate"

Click save

3) your done

 

c) Further steps

 

1) Try steps from a) to asure that the Problem is solved.

2) Use Nagios or an other supervision software to monitor you IPMI Ports.